1. Field of the Invention
The present invention relates to a pump device and a hydraulic actuator.
2. Description of the Related Art
In a hydraulic actuator used for changing the inclination of an outboard motor with respect to a hull or the like, a switching valve for switching the flow of hydraulic fluid to a lower chamber or an upper chamber is provided in a flow path between a pump and a cylinder device, the inside of which is segmented into the lower chamber (first chamber) and the upper chamber (second chamber) by a piston. The switching valve is configured such that an open valve on a side communicating with the lower chamber and an open valve on a side communicating with the upper chamber coordinate with each other. For each open valve, an actuation valve that slides within a valve chamber and a check valve are combined.
The switching valve operates in the following manner. When hydraulic fluid flows from the pump into the valve chamber of the open valve on the side communicating with the lower chamber, the check valve on the lower chamber side open under pressure of hydraulic fluid, and hydraulic fluid flows to the lower chamber. In parallel with the operation of the check valve, the actuation valve on the lower chamber side that is under pressure due to the hydraulic fluid flowing in is displaced within the valve chamber, and the pressure of the displaced actuation valve causes the actuation valve of the open valve on the side communicating with the upper chamber via a communication path to be displaced within the valve chamber. The displaced actuation valve on the upper chamber side pushes the check valve on the upper chamber side to open the check valve and return hydraulic fluid from the upper chamber to the pump.
When hydraulic fluid flows from the pump into the valve chamber of the open valve on the side communicating with the upper chamber, hydraulic fluid is sent to the upper chamber and hydraulic fluid is returned from the lower chamber to the pump by an operation opposite to that described above.
Conventionally, the valve chamber formed in a pump case accommodates each actuation valve, and a manifold on which the pump case is stacked accommodates the check valve such that the actuation valve to be combined with is opposed. At this time, each actuation valve is arranged to be displaced in the direction of stacking the pump case and the manifold (for example, see Japanese Patent Application Laid-open No. H7-228294).
[Patent Document 1] Japanese Patent Application Laid-open No. H7-228294